Impellers for impact printers

ABSTRACT

A plurality of self-restoring equally spaced apart print hammers selectively are driven lineally toward a printing position by continuously rotating impellers having equiangularly spaced radial impelling elements. Each impeller is effective through the agency of an interponent, which is selectively elevated into the path of associated impelling elements upon latching of the armature of an electromagnet, for transmitting impeller force to a corresponding print hammer. A plurality of dies, which are conveyed past the hammers for printing, are aligned axially of an endless conveyor in equally spaced relationship different from the spacing of said hammers. The impelling elements of each impeller are angularly offset from corresponding impelling elements of adjoining impellers in accordance with and for accommodation of the spacing difference.

United States Patent 1 1 Babler I i 1 IMPELLERS FOR IMPACT PRINTERS [75] -lnventor: Egon S. Babler, Northbrook, Ill.

[73] Assignees Teletype Corporation, Skokie, Ill. 22] Filed: July 3, 1972 21 Appl. No.:-268,236

I Prirnary ExdminerRobert E. Bagwill Assistant ExaminerE. M. Coven Attorney, Agent, or Firm-Sherman'P. Appel; John L. t

Landis p 57] i ABSTRACT A plurality of self-restoring equally spaced apart print hammers selectively are driven lineally toward a printing position by continuously rotating impellers having equiangularly spaced radial impelling elements. Each impeller is effective through the agency of an interponent, which is selectively elevated into the path of associated impelling elements upon latching of the armature of an electromagnet, for transmitting impeller force to a corresponding print hammer. A plurality of dies, which are conveyed past the hammers for printing, are aligned axially of an endless conveyor in equally spaced relationship different from the spacing of said hammers. The impelling elements of each impeller are angularly offset from corresponding impelling elements of adjoining impellers in accordance with and for accommodation of the spacing differ- 15 Claims, 4 Drawing Figures PATENTED 51974 SREEIIUFS 1 IMPELLERS FOR IMPACT PRINTERS BACKGROUND OF THE INVENTION The present invention relates to signal responsive impact printers having impellers selectively effective on print hammers. More particularly, the invention relates to the radial impellers in such printers effective through FIG. 4 is an exploded view of a section of a shaft for a group of impellers comprising impelling means in said printer.

DETAILED DESCRIPTION OF THE INVENTION Referring now to FIG. 1 of the drawings, the impact printer shown is generally designated 10. It has a pair of spaced apart pulleys 14 and 16 about which an endless carrier 12 is trained for translocating a plurality of pallets 18 by movement in a circuitous path. A plurality of dies 17 (FIG. 2) are carried on the front faces of the pallets, the latter being uniformly dimensioned and uniformly and equally spaced apart axially of the carrier. When the dies comprise alphanumeric characters, two

5 or more successive fonts axially of carrier l2may enages of a plurality of characters to be reproduced substantially simultaneously on a line. The printer output is known as line-at -a-tirne printing.

It is an object of the present invention to provide a novel impact printer. I

It is another object of the invention to provide novel radial impeller means in an impact printer.

It is a further object of the invention to maximize printing speed in an impact printer having radial impellers.

SUMMARY OF THE INVENTION To attain the foregoing, and other objects of the invention which will become apparent from the ensuing detailed description, each impeller, of a plurality of continuously driven impellers, is offset from the others thereof for'imposing impelling forces in succession on hammers upon hammer alignment with dies for printing. The hammers are equally spaced apart in an array in an impact printer. An array of pallets, which carry the dies, also are equally spaced apart, though their spacing is different from the spacing of the hammers. And the pallets and the hammers are relatively movable for aligning pallets in succession with successive hammers for printing.

BRIEF DESCRIPTION OF THE DRAWINGS In the ensuing detailed description of the drawings,

A reference is had to the accompanying drawings on which:

able longer line output.

Carrier 12 and pallets 18, together with their mountings may be substantially as shown and described in the copending application of Francis E. Huntoon and James F. Kearney, Ser. No. 208,198, filed Dec. 15, 1971, now US. Pat. 3,742,848 and assigned to the assignee of the present application. In accordance with said copending application, the plane in which parallel axes of pulleys 14 and 16 are disposed and the vertical section 20 of web 22 on which printing is about to occur are orthogonally disposed. Such arrangement generates a loop in the carrier with an upper or printing.

course 211 and a lower or return course 23 which are disposed in a plane which is substantially parallel to the web section 20. g

In the exemplary printer l0, pulley 14 is an idler sheave while pulley 16 is a drive sheave secured to a shaft 24. Driving torque continuously is transmitted to shaft 24 from an operating prime mover means, herein shown as a motor 26, through a drive train generally designated 28. The latter herein includes an impeller shaft 30. This shaft is continuously driven in the direction indicated by arrow 31 during printer operation.

A segment 32 of ribbon 34 is disposed in a plane substantially parallel to carrier course 21 between and spaced slightly from face 36 of web section 20 and the pallets 18 supported from said last course. The ribbon is trained about a plurality of ribbon guides 38 which are spaced apart such that the ribbon assumes a generally rectangular configuration in a horizontal plane. Opposed end portions of the ribbon are secured to a pair of adjoining ribbon spools 40 and 42 which alternately function for ribbon supply and accummulation. They alternately are driven in opposite angular directions, by a spool control mechanism 44, the details of construction of which form no part of the present invention. Mechanism 44 is connected to motor 26 by a pulley wheel 46, disposedin a common plane with spools 4t) and 42. It is secured on an end portion 47 of shaft 24 for driving the spool control mechanism through a pulley belt 48. v

A clutch 50, which may be conventional, is mounted for releaseably securing the split shaft section 52 to the shaft 24 from which said section extends axially. Selective actuation of the clutch may be effected through logic (not shown) which may be conventional and the details of construction of which form no part of the invention. Thereupon, operating means, being a drive train generally designated 54, advances web 22, in the direction shown by arrow 56, a line at a time. Such advancement results from incremental rotation of a worm gear 58 for driving a pulley belt 60 intermittently angularly to move a cylindrical roller 62. Roller 62 is disposed transversely of and adjacent to the path of web movement for frictionally engaging web 22 and in cooperation with other components (not shown), intermittedly drawing said web from its supply source (not shown) about a guiding cylinder 64, as said web is advanced.

In accordance with one aspect of the invention, impelling means comprises an array of radially symmetrical impellers 66 (only representative ones of which are shown in FIG. 1). Each impeller is comprised of a plurality of radial, equiangularly spaced teeth or impelling elements 68, the impellers being concentrically secured to shaft 30 for rotation therewith in the direction shown by arrow 70 (FIG. 2), in the exemplary embodiment. The impellers are axially or horizontally spaced such that each is disposed in substantially horizontal alignment with a printing station on an imaginary line extending horizontally across web section 20. Opposed end portions of the shaft 30 are journalled in spaced apart vertical side members 72 (only one is shown in FIG. 2) of the frame or chassis 74 of printer 10. Impacter means for printing comprise a plurality of hammers 76 (only some of which are shown in FIG. 1) disposed behind back face 78 (FIG. 2) of web section 20. Each hammer is aligned with the others in a horizontal array parallel to the alignment of impellers 66. Each hammer also is aligned with, though spaced from, and disposed out of the path of 'movement of an associated impeller by which it can be driven in a lineal path, perpendicularly to web section 20, between a normal or non-printing position (FIG. I) and a printing position (dashed line of FIG. 3) against said back face 78 (FIG. 2).

The dies 17 on pallets 18 in course 21 and hammers 76 are disposed at a common horizontal level; and said pallets and their dies when translocated move in a path parallel to the hammer array for printing. Thereby, each pallet 18 and groups thereof can be moved succesively into printing positions in horizontal alignment with successive hammers 76 and groups thereof. The force generated by each impeller 66 for urging web section 20, ribbon segment 32 and any aligned dies 17 into contact is of sufficient magnitude for printing by forming an image of each such die on web face 78.

A horizontal bumper in theform of a rod 80 is disposed parallel to shaft 30 has opposed ends secured in the chassis sides 72. Said rod extends through horizontally aligned slots 82 in the hammers 76 for limiting horizontal hammer movement.

A leaf spring 84 (FIG. 2), of general vertical orientation and associated with each hammer 76, is included in hammer driving means. It has a lower end portion which is rigidly secured to a front chassis plate 86 and an upper end portion-engaged in a downwardly opening slot 88 in the printing head 77 of each hammer 76. Each spring has a slightly tensioned condition (FIG. 2)

I during which its hammer is in its rearward or most reshown and described in my copending application Ser. No. 268,238, filed contemporaneously herewith. As shown in said last named application, the interponents are disposed in general horizontal alignment and each has: l a first or upper position in which it is in a projected condition, with its upper free end portion disposed inv the path of movement of associated impelling elements 68 for transmitting force from its impeller 66 to an aligned hammer 76 in consequence of which printing occurs, and (2) a lower, non-printing, or second position in which said interponent has fallen and is removed from the impeller path.

As shown and described in said last named application, each interponent 90 intermittently is controlled by an electromagcet assembly comprised of a magnetically latchable armature 92 and an electromagnet 94 (FIG. 2). Any suitable logic (not shown and forming no part of the present invention) which may be conventional may be employed for energizing selected of said electromagnets 94. In consequence of energization of any electromagnet its armature will be rocked, magnetomotively, against the restoring bias of its spring 96 clockwise from its position shown (FIG. 2) to a latched position (no'tshown).

correspondingly, an affected interponent will be thrust upwardly (from its FIG. 2 position) into its first position or projected condition (not shown) between a pair of adjoining impelling elements 68 against the lowering bias of an associated spring 98 which becomes tensioned upon upward movement of its interponent. Ensuingly, the upwardly thrust interponent will be engaged by a circuitously traveling impelling element 68 and rocked into engagement with an associated har'nmer 76 to effect momentum transfer and translation of impeller torque into a lineal force for printing. In the exemplary printer 10, both momentum transfer and .restoration of an interponent to its second position practice in line-at-a-time printers of the instant class. It

permits the use of hammers having heads 77 of widths greater than the pallet widths to accommodate slight misalignment during printing, and it enables minimization of spacing of dies and pallets, while preventing smudging resulting from web contact with non-selected dies 17 adjoining each selected or printing die.

However, the aforedescribed arrangement precludes intentional actuation of adjoining impelling means. As shown (FIG. 3), only hammers from groups comprised of every third hammer (e.g. 76A) should be actuated simultaneously, in the illustrated embodiment. To accommodate this requirement, impellers are arranged in adjoining sets of three adjoining impellers 66A, 66B, and 66C (FIG. 4). Satisfactory high speed printing can be produced with a printer 10 having: (1) pallets 18, each 0.090 inches in width, with spacing of pallet centers axially of course 21 of 0.150 inches and (2) hammers 76 whose heads 77 are 0.097 inches wide and the distance between hammer centers is 0.100 inches, and

3 wherein a set ofthree hammers 76A, 76B, and 76C (FIG. 3) is as wide as a set of two pallets 18X, and I8Y.

In accordance with the present invention, the group of impelling elements 68 comprising each of impellers 66A, 66B, and 66C is offset from another group for imposing imp'eller forces on the hammers in succession upon alignment with pallets for printing. More particularly, each impelling element of each of the impellers 66A, 66B, and 66C is angularly offset from a corresponding impelling element of an adjacent impeller. In the instant embodiment the impelling elements 68 of impeller 66B are angularly offset (retarded) from the impelling elements of impeller 66A by one-third of the angular distance D (FIG. 4) between impelling elements of impeller 66A, by angle Zqb in FIG. 4; and the impelling elements of impeller 66C are offset from the impelling elements of impeller 66A by two-thirds of the angular'distance between the impelling elements of impeller 66A, by angle 2gb in FIG. 4, as will be described hereinafter in the examples relating to FIGS. 3 and 4.

Correct angular disposition or setting results from mounting impellers 66A, 66B, and 66C relative to a center line 100 with respect to which offset of the impelling elements is measured. Splining of the hubs of the impellers as at 102 (FIG. 3 for keying Ol'l shaft 30, insures accuracy of the settings. As described in my copending application Serial No. 268,238, the impellers 66A, 66B, and 66C are spaced along the shaft 30 the require distances, equal to the spacing of the hammers 18, by a plurality of spacers or shims 97, one of which is shown in FIG. 2. The shims are circular, and concenmove 0.050 inches. During such period, one half of the pallets 18 will move from a disaligned condition into printing alignment with one third of the hammers.

To clarify the printing sequence, assume that impellers 66A are aligned for control of hammers 76A; and that one associated interponent 90 has been elevated 'for printing and has been struck as a corresponding element 68 reached zero line 100. Thereupon, its hammer 76A will be impelled for printing (to the phantom position of FIG. 3) with a pallet 18X all of which will then have reached positions of alignment with hammers 76A. Thereafter, as carrier 21 moves a distance of 0.050 inches, in the direction shown by arrow 104 (FIG. 3), pallets I8Y will become aligned for printing with hammers 76B. Simultaneously with such last carrier movement, the impelling elements 68 of each impeller 668 will have moved one-third the angular distance between adjoining impeller elements 68 to reach the zero line 100 immediately before pallets I8Y become aligned with hammers 768 for actuating an interponent associated with the hammers 768 which may have been elevated. As the carrier moves 0.050 inches further, pallets 18X will become aligned for printing with hammers 76C. These latter are aligned for printing with impellers 66C whose elements 68 will have moved to zero line 100 as pallets 18X move into alignment with hammers 76C.

In the illustrated embodiment all the pallets 18X will be simultaneously aligned for pringing with hammers 76A, while the remaining hammers and pallets will be disaligned for printing. Following the next increment of movement all of the pallets ISY will be simultaneously aligned for printing with hammers 768, while the pa]- lets ISX will be disaligned for printing. Thereafter, the pallets 18X will again become aligned for printing, but with pallet hammers 76C, while the pallets ISY will be disaligned for printing. Next pallets I 8Y will become aligned for'printing, but with hammer 76A. In consequence of the foregoing, the hammers 76A, 76B and 76C are adapted to print in succession. That is to say, the hammers 76B and 76C will not print while a hammer 76A is printing. Hammers 76A and 76C will not print while any hammer 76B is printing. While a hammer 76C is printing, no hammer 76A or 76B will print. Thus, in the specific example described, using the reference characters in FIGS. 3 and 4, the type pallets 18 advance from bottom to top in FIG. 3 as indicated by arrow 104 (left to right in FIG. 1) at a constant speed set by the drive motor 26,- drive train 28, and drive sheave 16, as previously described. As the pallets 18 advance, they travel past the hammers '76 in the order C, B, A (from bottom to top in FIG. 3), but the hammers fire in the inverse order A, B, C, as described in the preceding paragraphs. Thus, in this embodiment, the hammers 76 fire in a sequence opposite to the direction of pallet flight. Correlating FIG. 4 with FIG. 3, the impellers 66A, for example, are first ready to fire, to print any and all selected characters in the type line aligned with the corresponding hammers 76A; followed by impellers 66B, retarded one-third of a tooth from 66A; followed by impellers 66C, retarded one third tooth behind B and two-thirds tooth behind A; followed again by impellers 66A, the next teeth 68 of which are retarded one-third tooth behind 66C, etc., in a continuous succession. Looking in the direction of pallet flight, the impellers 66 are arranged in the sequence 66C, 66B, 06A proceeding up the page in FIG. 3, aligned with the inner ends of the corresponding hammers 76C,

76B, and 76A as previously described, or in C, B, A

order proceeding from left to right in FIG. I, which is also the direction of pallet travel in the printing course 21.

Preferred means for sequential firing of the hammers for printing are as disclosed in my copending application Ser. No. 268,237, filed contemporaneously herewith.

As many modifications in the described construction could be conceived, and as many widely different embodiments could be made without departing from the spirit and scope of the claims, it is intended that all mat ter contained in the accompanying specification shall be considered as illustrative onlyand not in a limiting sense.

I claim:

1. In an impact printer of the class having a row of print hammers equally spaced apart a first distance and an array of type pallets equally spaced apart a second distance and arranged with the array of hammers for relative movement for simultaneously aligning successive pallets with successive hammers for printing; impelling means having a plurality of impelling elements projecting therefrom; means for mounting the impelling means parallel to the row of hammers; means for continuously driving the impelling means so that the impelling elements repeatedly pass a printing position adjacent one end of each hammer; interponent means responsive to printing signals for interposition between 'the impelling means and a selected hammer so that upon passing the printing position the next advancing impelling element strikes the interponent means to drive the selected hammer into printing engagement with a type pallet then aligned with the print hammer; an improved assembly characterized by:

a single row of individual impellers, an individal impeller being provided for and associated with each print hammer and each impeller having a plurality of equally spaced apart impelling elements projecting therefrom; and

means for mounting the impellers so that the impelling elements of adjacent impellers in the row are offset from one another by amounts proportional to the different spacing between hammers and the type pallets so that, when one impeller element on one impeller is in printing position and its asso' ciated hammer is aligned with a type pallet, the impelling elements on the two adjacent impellers are not in printing position.

2. A printer assembly as recited in claim 1 wherein:

at least six impellers are provided, one corresponding to each possible printing position in a column to be printed, the impellers comprising a plurality of generally circular discs, each of the same size and having an equal plurality of equally spaced teeth projecting radially therefrom; and

the mounting means comprises single shaft on which the impellers are individually fixed at equally spaced intervals along the length thereof, for rotation therewith, the impellers being positioned on the shaft such that the teeth of every third impeller are aligned with each other, and the ones in between are offset from each other by equal angles corresponding to whole numbers of thirds of a tooth, so that every third impeller is aligned to print at one instant, after which the next set of three is aligned to print, etc.

3. A printer as recited in claim 2, wherein the type pallet spacing is l /2 times that of the impeller spacing.

4. A printer as recited in claim 3 wherein each impeller is moved at a preselected angular velocity so that each impeller tooth moves one-third of the angular distance between adjacent teeth during the time period required to move one-half of the pallets from a position of non-alignment with one-third of the hammers to a position of printing alignment with that one-third of the hammers.

5. A line-at-a-time teleprinter comprising:

a group of at least six print hammers mounted in a row and spaced equal distances corresponding to the spacing between adjacent characters in a line of type to be printed, one print hammer being provided for each possible character to be printed in the line;

an endless carrier bearing type elements, the type elements being spaced along the length of the carrier a distance greater than the spacing between adjacent hammers;

means for mounting the carrier so that a printing course of the carrier is disposed in closely spaced parallelism with printing ends of the hammers, and

for driving the carrier so that the type elements hammers;

a group of at least six continuously rotating impeller wheels mounted in a row, each impeller wheel having a plurality of equally spaced teeth for selectively actuating the print hammers when a character is to be printed, a separate impeller being provided for each printing mechanism and the impeller wheels being spaced in the row equal distances corresponding to the spacing between the print hammers; and

means for mounting the impeller wheels so that the teeth of all impeller wheels in the row are angularly displaced from the teeth of the adjacent wheels in the row by predetermined angles preset in accordance with the spacing of the type elements so that no two consecutive hammers can be actuated at the same instant and so that each hammer in' the sequence can be actuated each time a type element on the carrier is momentarily aligned with the hammer.

6. A lin-at-a-time teleprinter as recited in claim 5 wherein:

the type elements on the endless carrier are spaced apart a distance equal to 1 Va times the spacing of the impeller wheels; and

the teeth of all impeller wheels in the row are angularly displaced from the teeth of the adjacent wheels in the row by predetermined angles preset so that the teeth on every wheel are aligned with those on the third wheel distant from it.

7. In combination with a teleprinter of the type having a plurality of individual printing mechanisms mounted in a row and spaced equal distances corresponding to the spacing between adjacent characters in a line of type to be printed, an improved actuating mechanism comprising:

a plurality of continuously rotating impeller wheels equal in number to the number of printing mechanisms, each impeller wheel having a plurality of equally spaced teeth for selectively striking a firing portion of an associated printing mechanism when a character is to be printed, a separate impeller wheel being provided for each printing mechanism; and

means for mounting the impeller wheels in a single row so that the impeller wheels are spaced the same distances as the printing mechanisms and so that the teeth of all impeller wheels in the row are angularly displaced from the teeth of the adjacent wheels in the row by preset angles so that no two adjacent printing mechanisms can be actuated at the same time, but so that adjacent printing mechanisms are actuable in a timed sequence based on the angular displacement of the impeller teeth.

8. A teleprinter as recited in claim 7, wherein the impeller wheels are arranged in groups of N, proceeding along the row of impeller wheels, N being a whole number greater than 2, each Nth impeller wheel in the row having its teeth aligned with every other Nth wheel so that all Nth impeller wheel are arranged to print at the same instant, each group of impeller wheels in the row having their teeth retarded by l lNth of the pitch length of the impeller wheels from another group of impeller wheels in a pattern so that each group is aligned to print at a later instant than a preceding group by a time set by the time required for the impeller wheels to travel l/Nth of a tooth.

9. A teleprinter as recited in claim 8, wherein:

the printing mechanism includes a row of type hammers mounted parallel to each other and parallel to the row of impeller wheels, one type hammer being associated with each separate impeller wheel and the manners being spaced the same distance from each other as the impeller wheels, and a plurality of type elements mounted on an endless carrier for continuous movement past the type hammers along a line parallel to the line of the row of hammers, the type elements being spaced along the carrier a distance greater than the spacing between hammers according to a selected ratio of whole numbers, so that one fraction of the type eleni ents align with a smaller fraction of the hammers t successive instants as thetype elements advan past the hammers. i

10. A teleprinter as recited in claim 9, wherein the widths of the heads of the print hammers are greater than the widths of the type elements (width referring to the dimension parallel to the line of flight of the type elements).

11. A teleprinter as recited in claim 10, wherein there are three impeller groups (N=3) and two type element groups, the type elements being spaced 1 /.2 times as far apart as the'impellers, and in which the angle of retardation of successive impeller teeth is one-third of a tooth.

i 12. A teleprinter as recited in claim 7, wherein the mounting means comprises:

an elongated rotatable shaft on which the impeller wheels are mounted in a single row;

means for individually positioning the impeller wheels on the shaftfor rotation therewith while maintaining the preset angular displacement of the teeth of adjacent impeller wheels in the row; and

a plurality of spacers mounted between adjacent impeller wheels for spacing the impeller wheels along the shaft at intervals corresponding to the spacing of the printing mechanisms.

13. A teleprinter as recited in claim 12, wherein the spacers comprise circular shims concentrically mounted on the shaft between adjacent impeller wheels and having a radius greater than that of the impeller teeth.

14. A teleprinter as recited in claim 13, wherein the printing mechanisms comprise a plurality of individual print hammers mounted in a row parallel to the row of impeller wheels and spaced the same distances as the impeller wheels, each print hammer having an inner, firing end positioned adjacent to the impeller wheels and received between and guided by adjacent shims on the shaft.

15. A teleprinter as recited in claim 14, wherein the printer mechanisms further comprise:

a plurality of interponents equal to the number of impeller wheels, and print hammers;

means for mounting the interponents in a single row parallel to the impeller wheels and print hammers, with the interponents spaced the same distances as the impeller wheels and print hammers and with each interponent being aligned with both a corresponding impeller wheel and a corresponding print hammer, each interponent having an outer, firing end positioned adjacent to the corresponding impeller wheel and received between and guided by adjacent shims on the shaft; and means for selectively actuating the interponents when a character is to be printed, for moving the outer end of the interponent into the path of an oncoming impeller tooth, the impeller teeth and the interponents being so positioned with respect to the print hammers that the impeller tooth strikes the outer end of the interponent, which then strikes the inner end of the corresponding hammer to print a character.

=l l l l 

1. In an impact printer of the class having a row of print hammers equally spaced apart a first distance and an array of type pallets equally spaced apart a second distance and arranged with the array of hammers for relative movement for simultaneously aligning successive pallets with successive hammers for printing; impelling means having a plurality of impelling elements projecting therefrom; means for mounting the impelling means parallel to the row of hammers; means for continuously driving the impelling means so that the impelling elements repeatedly pass a printing position adjacent one end of each hammer; interponent means responsive to printing signals for interposition between the impelling means and a selected hammer so that upon passing the printing position the next advancing impelling element strikes the interponent means to drive the selected hammer into printing engagement with a type pallet then aligned with the print hammer; an improved assembly characterized by: a single row of individual impellers, an individal impeller being provided for and associated with each print hammer and each impeller having a plurality of equally spaced apart impelling elements projecting therefrom; and means for mounting the impellers so that the impelling elements of adjacent impellers in the row are offset from one another by amounts proportional to the different spacing between hammers and the type pallets so that, when one impeller element on one impeller is in printing position and its associated hammer is aligned with a type pallet, the impelling elements on the two adjacent impellers are not in printing position.
 2. A printer assembly as recited in claim 1 wherein: at least six impellers are provided, one corresponding to each possible printing position in a column to be printed, the impellers comprising a plurality of generally circular discs, each of the same size and having an equal plurality of equally spaced teeth projecting radially therefrom; and the mounting means comprises s single shaft on which the impellers are individually fixed at equally spaced intervals along the length thereof, for rotation therewith, the impellers being positioned on the shaft such that the teeth of every third impeller are aligned with each other, and the ones in between are offset from each other by equal angles corresponding to whole numbers of thirds of a tooth, so that every third impeller is aligned to print at one instant, after which the next set of three is aligned to print, etc.
 3. A printer as recited in claim 2, wherein the type pAllet spacing is 1 1/2 times that of the impeller spacing.
 4. A printer as recited in claim 3 wherein each impeller is moved at a preselected angular velocity so that each impeller tooth moves one-third of the angular distance between adjacent teeth during the time period required to move one-half of the pallets from a position of non-alignment with one-third of the hammers to a position of printing alignment with that one-third of the hammers.
 5. A line-at-a-time teleprinter comprising: a group of at least six print hammers mounted in a row and spaced equal distances corresponding to the spacing between adjacent characters in a line of type to be printed, one print hammer being provided for each possible character to be printed in the line; an endless carrier bearing type elements, the type elements being spaced along the length of the carrier a distance greater than the spacing between adjacent hammers; means for mounting the carrier so that a printing course of the carrier is disposed in closely spaced parallelism with printing ends of the hammers, and for driving the carrier so that the type elements continuously pass and face the printing ends of the hammers; a group of at least six continuously rotating impeller wheels mounted in a row, each impeller wheel having a plurality of equally spaced teeth for selectively actuating the print hammers when a character is to be printed, a separate impeller being provided for each printing mechanism and the impeller wheels being spaced in the row equal distances corresponding to the spacing between the print hammers; and means for mounting the impeller wheels so that the teeth of all impeller wheels in the row are angularly displaced from the teeth of the adjacent wheels in the row by predetermined angles preset in accordance with the spacing of the type elements so that no two consecutive hammers can be actuated at the same instant and so that each hammer in the sequence can be actuated each time a type element on the carrier is momentarily aligned with the hammer.
 6. A lin-at-a-time teleprinter as recited in claim 5 wherein: the type elements on the endless carrier are spaced apart a distance equal to 1 1/2 times the spacing of the impeller wheels; and the teeth of all impeller wheels in the row are angularly displaced from the teeth of the adjacent wheels in the row by predetermined angles preset so that the teeth on every wheel are aligned with those on the third wheel distant from it.
 7. In combination with a teleprinter of the type having a plurality of individual printing mechanisms mounted in a row and spaced equal distances corresponding to the spacing between adjacent characters in a line of type to be printed, an improved actuating mechanism comprising: a plurality of continuously rotating impeller wheels equal in number to the number of printing mechanisms, each impeller wheel having a plurality of equally spaced teeth for selectively striking a firing portion of an associated printing mechanism when a character is to be printed, a separate impeller wheel being provided for each printing mechanism; and means for mounting the impeller wheels in a single row so that the impeller wheels are spaced the same distances as the printing mechanisms and so that the teeth of all impeller wheels in the row are angularly displaced from the teeth of the adjacent wheels in the row by preset angles so that no two adjacent printing mechanisms can be actuated at the same time, but so that adjacent printing mechanisms are actuable in a timed sequence based on the angular displacement of the impeller teeth.
 8. A teleprinter as recited in claim 7, wherein the impeller wheels are arranged in groups of N, proceeding along the row of impeller wheels, N being a whole number greater than 2, each Nth impeller wheel in the row having its teeth aligned with every other Nth wheel so that all Nth impeller wheel are arranged to print at the same instant, eAch group of impeller wheels in the row having their teeth retarded by 1/Nth of the pitch length of the impeller wheels from another group of impeller wheels in a pattern so that each group is aligned to print at a later instant than a preceding group by a time set by the time required for the impeller wheels to travel 1/Nth of a tooth.
 9. A teleprinter as recited in claim 8, wherein: the printing mechanism includes a row of type hammers mounted parallel to each other and parallel to the row of impeller wheels, one type hammer being associated with each separate impeller wheel and the manners being spaced the same distance from each other as the impeller wheels, and a plurality of type elements mounted on an endless carrier for continuous movement past the type hammers along a line parallel to the line of the row of hammers, the type elements being spaced along the carrier a distance greater than the spacing between hammers according to a selected ratio of whole numbers, so that one fraction of the type elements align with a smaller fraction of the hammers at successive instants as the type elements advance past the hammers.
 10. A teleprinter as recited in claim 9, wherein the widths of the heads of the print hammers are greater than the widths of the type elements (''''width'''' referring to the dimension parallel to the line of flight of the type elements).
 11. A teleprinter as recited in claim 10, wherein there are three impeller groups (N 3) and two type element groups, the type elements being spaced 1 1/2 times as far apart as the impellers, and in which the angle of retardation of successive impeller teeth is one-third of a tooth.
 12. A teleprinter as recited in claim 7, wherein the mounting means comprises: an elongated rotatable shaft on which the impeller wheels are mounted in a single row; means for individually positioning the impeller wheels on the shaft for rotation therewith while maintaining the preset angular displacement of the teeth of adjacent impeller wheels in the row; and a plurality of spacers mounted between adjacent impeller wheels for spacing the impeller wheels along the shaft at intervals corresponding to the spacing of the printing mechanisms.
 13. A teleprinter as recited in claim 12, wherein the spacers comprise circular shims concentrically mounted on the shaft between adjacent impeller wheels and having a radius greater than that of the impeller teeth.
 14. A teleprinter as recited in claim 13, wherein the printing mechanisms comprise a plurality of individual print hammers mounted in a row parallel to the row of impeller wheels and spaced the same distances as the impeller wheels, each print hammer having an inner, firing end positioned adjacent to the impeller wheels and received between and guided by adjacent shims on the shaft.
 15. A teleprinter as recited in claim 14, wherein the printer mechanisms further comprise: a plurality of interponents equal to the number of impeller wheels, and print hammers; means for mounting the interponents in a single row parallel to the impeller wheels and print hammers, with the interponents spaced the same distances as the impeller wheels and print hammers and with each interponent being aligned with both a corresponding impeller wheel and a corresponding print hammer, each interponent having an outer, firing end positioned adjacent to the corresponding impeller wheel and received between and guided by adjacent shims on the shaft; and means for selectively actuating the interponents when a character is to be printed, for moving the outer end of the interponent into the path of an oncoming impeller tooth, the impeller teeth and the interponents being so positioned with respect to the print hammers that the impeller tooth strikes the outer end of the interponent, which then strikes the inner end of the corresponding hammer to print a character. 